The present invention relates to an ATM (Asynchronous Transfer Mode) communication equipment and, more particularly, to a multilayer ATM communication equipment for forming a large-scale network at a low cost.
A conventional ATM communication equipment realizes high-speed data transfer by setting connection from a source to a destination before data transfer. With diversification of communication purposes and an increase in communication amount, however, the overhead for connection setting before data transfer cannot be neglected.
In contrast to this, there has been proposed an ATM communication equipment which can perform high-speed data transfer by using routing information on layer 3 as a network layer in connection setting, and uses a scheme of easily realizing connection setting to generate a shortcut path. For example, this technique is applied to an ATM communication equipment using the IFMP (Ipsilon Flow Management Protocol) of RFC (Request For Comments) 1954 of IETF (International Engineering Task Force).
The operation principle of this equipment will be described with reference to FIG. 14. Each switching node is composed of an ATM switch 1401 and an IP (Internet Protocol) controller 1402. At the start of transfer, since no shortcut path is set, a cell that has arrived at the ATM switch 1401 at the start of a data transfer flow and forms an IP packet is formed into an IP packet by the IP controller 1402. After this, an output port from which a cell is to be transferred is determined in accordance with the IP routing protocol, and cell transfer 1413 is performed from this output port to an adjacent switching node.
This IP controller 1402 identifies the flow of the packet, and assigns VPI (Virtual Path Identifier) information and VCI (Virtual Channel Identifier) information to the ATM cell in this flow when determining that the flow will continue for a long period of time. The IP controller 1402 then performs notification 1414 to the upper switching node located on the transmission side of this flow. When the notification of the assignment of the VPI and the VCI to the ATM cell in this flow is notified from the downstream switching node located on the reception side of the flow, the VPI and the VCI notified to the upstream side are made to correspond to the VPI and VCI notified from the downstream side, and a shortcut path 1415 is set in the ATM switch 1401.
Subsequently, the PI packet belonging to this flow is transferred as an ATM cell to an output port 1416 through the set shortcut path without being formed into an IP packet by the IP controller 1402. This shortcut path is canceled by monitoring the traffic and detecting that the same flow does not arrive for a predetermined period of time.
It is also important to construct a large-scale network by using such a communication equipment. As a communication equipment for constructing this large-scale network, a communication equipment using the STA (Spanning Tree Algorithm) of avoiding a loop in a network by performing route selection control between a plurality of bridges is available.
According to the communication equipment in xe2x80x9cNetwork Construction Methodxe2x80x9d in Japanese Patent Laid-Open No. 6-350606, a large-scale network is constructed by forming a tree by using the STA of a lower bridge relative to a reception bridge on the basis of a time value obtained when a predetermined data frame is received and a predetermined timeout value.
According to xe2x80x9cSpanning Tree Port Management Methodxe2x80x9d in Japanese Patent Laid-Open No. 8-195770, upon detection of a change in the connected state of a plurality of networks, ports which are not to be connected to the networks are disconnected, thereby preventing double relay operation even if the STA is used when a plurality of networks are connected to each other.
When data transfer on layer 2 as a data link layer is performed through a route based on the STA while a plurality of networks are connected to each other, transfer on layer 2 as a data link layer is performed concurrently with data transfer on a network layer after a given port is blocked, and a route is selected by the RIP (Routing Information Protocol). As a result, a heavy load is imposed on this system. In order to prevent this, the xe2x80x9cInter-LAN Connection Apparatusxe2x80x9d in Japanese Patent Laid-Open No. 5-235943 can operate a metric value for this port when route setting is to be performed on layer 3, thereby reducing the load.
According to the xe2x80x9cBridge Apparatus and Network Construction Methodxe2x80x9d disclosed in Japanese Patent Laid-Open No. 5-235945, when networks with different data link protocol links on the data link layers are to be connected to each other, connection between different protocols can be performed by using data link protocol processing means equal in number to the bridge apparatuses.
The xe2x80x9cMAC Bridge Control Systemxe2x80x9d disclosed in Japanese Patent Laid-Open No. 5-22294 includes several learning tables such as a port number/MAC (Media Access Control) address table. In this system, when different types of networks, especially a high-speed network and a low-speed network, are connected to each other, and information corresponding to a frame to be transferred cannot be obtained from these learning tables, the frame is discarded, thereby preventing unnecessary traffic in the low-speed network.
A conventional multilayer ATM communication equipment can set a connection serving as a shortcut path used only to exchange information about assignment of a VPI and a VCI to a flow between adjacent switch nodes. However, IP routing protocol processing must be performed for all the switching nodes, requiring a complicated, expensive equipment.
In addition, like a general router, this equipment must set a sub-network indicated by an IP address for each input/output port, and the arrangement of the sub-network is limited by the input/output port of a node. For this reason, when a network terminal moves, re-setting of the IP address of the network terminal and the like must be performed.
It is an object of the present invention to provide an inexpensive communication equipment which can construct a large-scale network without making all switching nodes have a layer 3 routing protocol processing function.
It is another object of the present invention to provide a communication equipment which can make a network have flexibility by obviating the necessity for, for example, re-setting of the IP address of a network terminal upon movement of the network terminal.
In order to achieve the above objects, according to the present invention, there is provided a multilayer ATM communication equipment comprising an input port for inputting an ATM cell as transfer input data, an output port for outputting the ATM cell as transfer output data, port information storage means in which transfer route information for determining a transfer route of the ATM cell input from the input port, and input port information and output port information which respectively correspond to the transfer route information are stored, ATM transfer output means for transferring/outputting the ATM cell from an output port corresponding to the output port information stored in the port information storage means on the basis of the transfer route information in the input ATM cell and an input port number corresponding to the input port from which the ATM cell is input, MAC frame forming means for forming the ATM cell input from the input port into an MAC frame on an MAC layer as one of constituent elements of a data link layer of the ATM cell input from the input port, on the basis of the transfer route information in the ATM cell, flow information storage means in which flow information as information corresponding to each of destination information and source information in the ATM cell input from the input port, and transfer output information for transferring/outputting the ATM cell in accordance with the flow information are stored, flow transfer means for, when transfer output information corresponding to the flow information of the MAC frame formed by the MAC frame forming means is stored in the flow information storage means, transferring/outputting the MAC frame from the output port on the basis of the transfer output information, MAC address storage means in which destination information of the MAC frame and transfer output information corresponding to the destination information are stored, and MAC layer transfer output means for, when transfer output information corresponding to destination information in an MAC frame is stored in the MAC address storage means, transferring/outputting the MAC frame from the output port on the basis of the transfer output information corresponding to the MAC frame, and when the transfer output information is not stored in the MAC address storage means, assigning a new input port, notifying a transmission-side switch of the flow information of the MAC frame and the assigned input port, setting a shortcut path on the basis of an output port notified from a reception-side switch, and transferring/outputting the MAC frame from the notified output port.